The invention relates to a process for the preparation of novel, partially crystalline polyether polyols having a hydroxy functionality of xe2x89xa72 and to the new polyether polyols and the use thereof.
It is known from the literature that products with improved mechanical properties may be synthesised with crystallising polyether polyols based on propylene oxide having a functionality of 2 according to the isocyanate-polyaddition process (J. of Polymer Sci. (Polym. Chem. Ed.) Vol. 15, 1655ff (1977)). The preparation of crystalline hydroxyfunctional dihydroxy polyethers from isotactic polypropylene glycols by ozonolysis followed by hydrogenation with moisture-sensitive and oxygen-sensitive reagents and fractionation is extremely laborious and permits little variability. The object was, therefore, to provide a broad range of crystalline hydroxy polyethers having a functionality of xe2x89xa72 which are suitable, e.g. for PUR synthesis, according to a less laborious process with a large potential for variation.
It is also known that bimetallic xcexc-oxoalkoxides are suitable for the polymerisation of propylene oxide to crystallising polyether polyols U.S. Pat. No. 3,432,445, Polym. Preprints 218 (1984)). No references to the preparation of polyether polyols having a suitable hydroxy functionality which are suitable as chain extenders and crosslinking agents for isocyanate polyaddition can be derived from the publication.
These bimetallic catalysts used for propylene oxide polymerisation contain monool substituents which are then incorporated in the polypropylene oxide during the polymerisation process, which leads to polypropylene oxides having a hydroxy functionality well below 2, which are unsuitable e.g. as chain extenders for the preparation of polyurethanes.
Surprisingly, it has now been found that, as a result of reacting bimetallic catalysts with hydroxyl compounds having a functionality of xe2x89xa72, catalysts are produced which permit the polymerisation of alkylene oxide to polyether polyols having a functionality of xe2x89xa72. The surprising aspect hereof is that the catalytically active bimetallic starting compounds which, according to the literature (J. of Polym. Sci.: Part A: Polym. Chem., 24, 1423 (1986)), are sensitive to impurities, are still active for alkylene oxide polymerisation after the reaction with hydroxyl compounds, even at temperatures of 100-160xc2x0 C.
Moreover, it could not have been foreseen that the bimetallic catalysts, which are to be regarded as polyfunctional with respect to hydroxyl compounds, do not crosslink or interconnect in the presence of hydroxyl compounds having a functionality of xe2x89xa72, and remain catalytically active.
The invention relates, therefore, to a process for the preparation of novel, partially crystalline polyether polyols having a hydroxy functionality of  greater than 2, which is characterised in that alkylene oxides are polymerised in the presence of bimetallic xcexc-oxoalkoxides corresponding to the formula (I)
(RO)x-1xe2x80x94M2xe2x80x94Oxe2x80x94M1xe2x80x94Oxe2x80x94M2xe2x80x94(OR)x-1xe2x80x83xe2x80x83(I)
wherein
R stands for a C1-C10 alkyl radical,
M1 stands for zinc, cobalt, molybdenum, iron, chromium or manganese,
M2 means aluminium or titanium and
x stands for 3 to 4,
wherein the xcexc-oxoalkoxides (I) were reacted beforehand with hydroxyl compounds corresponding to the formula (II) 
xe2x80x83in which
Q stands for a C2-C20 alkyl group,
R1 and R2, independently of one another, mean hydrogen or C1-C20 hydrocarbon radicals,
1 and n independently of one another, stand for numbers from 0 to 40, and
y means an integer from 2 to 6.
Suitable bimetallic xcexc-oxoalkoxides are preferably those in which M1 stands for zinc and M2 stands for aluminium, x is the number 3 and R stands for n- and isopropyl and also n-butyl.
The bimetallic xcexc-oxoalkoxides suitable for use in the process according to the invention are well known and described in more detail, for example, in the U.S. Pat. No. 3,432,445 mentioned above.
Particularly suitable hydroxyl compounds corresponding to formula (II) which are reacted with the bimetallic xcexc-oxoalkoxides used are those with a functionality of xe2x89xa72, preferably 2 to 6, which have an average molecular weight of 90 to 6000, preferably 90 to 2000. The average molecular weight is determined in the usual way by measuring the OH value or by GPC against polystyrene as a comparison.
Hydroxyl compounds corresponding to formula (II) include, in particular, polypropylene glycols, polyethylene glycols, polyethylene oxide polypropylene oxide block copolymers and random Cxe2x80x94Oxe2x80x94PO-copolymers, in addition to the well known low molecular weight polyhydroxyl compounds. Such compounds are described e.g. in Kirk-Othmer (3)1, 754 to 789.
More particularly preferred hydroxyl compounds include:
Butane-1,4-diol, diethylene glycol, dipropylene glycol, tripropylene glycol, and polypropylene glycols having an Mn of 200 to 2000 started on propylene glycol, butane-1,4-diol, glycerol, triiethylol propane or sorbitol, or copolymers of propylene oxide and ethylene oxide started on ethylene glycol, propylene glycol, butane-1,4-diol, glycerol or trimethylol propane having an Mn of 220 to 2000.
The reaction of the bimetallic xcexc-oxoalkoxide used corresponding to formula (I) with a hydroxyl compound corresponding to formula (II) takes place in such a way that 1 mole of polyol (II) is mixed with 5.10xe2x88x924 to 0.6, preferably 1.10xe2x88x923 to 0.3 mole of xcexc-oxoalkoxide and the mixture is heated for about 0.5 to 10 hours, preferably 2 to 5 hours, at about 100 to 150xc2x0 C., preferably 110 to 130xc2x0 C.
The reaction mixture is then stirred for a certain period (about 0.5 to 5 hours), optionally at a pressure below atmospheric, at elevated temperature (about 100 to 150xc2x0 C.).
The reaction mixture is then diluted with an organic solvent and/or diluent, e.g. a suitable hydrocarbon such as xylene and/or ligroin, preferably to 80 to 50 wt. %, and the solvent and/or diluent is then distilled again at reduced pressure (about 0.01 to 1013 mbar).
The bimetallic xcexc-oxoalkoxide thus modified with the polyols is then reacted with suitable alkylene oxides for the preparation of the partially crystalline polyether polyols. The reaction is carried out preferably at 20 to 200xc2x0 C., particularly at 80 to 150xc2x0 C., under normal or elevated pressure up to 20 bar.
Alkylene oxides suitable for such reactions are the well known alkylene oxides, preferably propylene oxide, 1,2-butylene oxide, epichlorohydrin, alkyl glycidyl ether and mixtures thereof. Propylene oxide and/or ethylene oxide is used in preference. Prior to the reaction with alkylene oxides, the modified xcexc-oxoalkoxide may be diluted with hydroxyl compounds having a functionality of xe2x89xa72, preferably with hydroxyl compounds corresponding to formula (II).
The reaction of the modified catalyst with the alkylene oxides may be carried out in bulk or in a suitable inert organic solvent such as toluene, xylene and/or tetrahydrofuran. The concentration and quantity of the solvent is chosen such that good control of the conversion reaction is possible under the given reaction conditions.
The modified bimetallic xcexc-oxoalkoxide is generally used in quantities of 5.10xe2x88x922 to 60 mole %, preferably in quantities of 0.1 to 20 mole %, based on the quantity of the polyether polyol to be prepared.
The new, partially crystalline polyether polyols with a functionality of xe2x89xa72, preferably 2 to 6, prepared according to the process of the invention, have average molecular weights Mn of 500 to 100,000, preferably 1000 to 10,000, determined by GPC against polystyrene or by means of the hydroxyl end group content (OH value), and have a molar proportion of isotactic triads determining the crystallinity of  greater than 28%, preferably  greater than 33%, determined by 13C-NMR spectroscopy.
The present invention also relates, therefore, to the new, partially crystalline polyether polyols of the kind described above.
The process according to the invention may be carried out both continuously and batchwise, for example, in a batch or semi-batch process.
According to the process of the invention, the crude product is worked up preferably by dissolving the polyether polyol prepared in a solvent such as toluene, xylene, tetrahydrofuran, ethyl acetate and/or methylene chloride.
The catalyst is then destroyed by acidified water and the reaction products are extracted with aqueous acid ( less than 25 wt. %), preferably with water. Preferably 1 to 2 acid equivalents are used to destroy the catalyst. Suitable acids include, i.a., hydrochloric acid, phosphoric acid, sulfuric acid, benzoic acid, acetic acid and/or lactic acid. Of course, other acids may also be used.
After intensive shaking with aqueous acid, the excess acid is removed by washing with water, optionally in the presence of a compound giving an alkaline reaction such as sodium bicarbonate. The polyol solution obtained is separated from the water, dried and the solvent is removed.
The product may be further purified by fractional precipitation under cold conditions from suitable solvents such as, e.g., acetone.
The partially crystalline polyether polyols prepared according to the process of the invention are outstandingly suitable for the preparation of polyurethane materials such as PUR elastomers, PUR foams and PUR coatings. The preparation of the above-mentioned PUR materials is well known and described, for example, in Kunststoff Handbuch, volume 7, 3rd edition, Carl-Verlag Verlag, 1993.